Monitoring the appearance of autoantibodies in the circulation has proven a reliable and robust approach to determining the onset of autoimmunity in type 1 diabetes (T1D). The progression of the disease is typically marked by the appearance of new autoantibody specificities rather than changes in existing antibody titer which possibly reflects a process of antigen epitope spreading and recruitment of a broader spectrum of auto reactive effector T-cells that ultimately reduce the [unreadable]-cell mass to a point where the pancreas is unable to deliver sufficient insulin to maintain metabolic control. Repositories of patient sera, lymphocytes and DNA from prospective natural history studies and therapeutic trials provide an invaluable resource for analyzing the process of initiation and progression of human T1D, and mechanistic information as to how the disease may be combated. Our proposal focuses on three targets of diabetes autoimmunity recently identified in our laboratory, namely molecularly-defined epitopes in Zn transporter 8, the H+/K+ ATPase subunit 4A, and IA-2PTP. It evaluates humoral immune responses on archived sera from participants in the recently-completed Diabetes Prevention Trial-1 and the ongoing Trialnet Natural History Study and associated ancillary studies (MMF/DZB and Rituximab trials). We aim to document the importance of these new biomarkers as predictive indicators of disease progression and their utility in recruitment of patients into therapeutic trials, as well as to gain insight into how best to monitor sequential events in immune dysregulation and impaired beta cell function that lead to disease. Our ultimate objective is not only to improve existing methods to predict risk of disease development but also to stage disease progression so as to direct decisions as to when and how to reinstate immune tolerance based on immunologic therapeutic intervention.